1. Field of the Invention
The present invention relates, generally, to a simplified in-mold article handling system, and more particularly, but not exclusively, the invention relates to an in-mold handling system that includes a simplified transmission for driving a slide across a molding face of an injection mold, between an inboard and an outboard position, for the handling of injection molded articles, such as lids, between their molding cavities and a drop chute, respectively.
2. Background Information
The advantages provided by an in-mold article handling system in accordance with the present invention are made apparent, for example, when incorporated into an injection molding system for the production of container lids. Accordingly, and without implying any such limitation on the general utility of the handling system, the in-mold handling system of the present invention will hereinafter be described within the context of an injection molding lid molding system.
Referring to FIG. 1, a lid molding system is shown that includes an injection molding machine clamp unit 34 with a four-level lid stack mold 36 mounted therein between a stationary platen 50 and a moving platen 52. The injection molding machine, clamp unit 34, and mold 36 being operable as commonly known. The clamp unit is further shown as including a clamp assembly 54 for operating the injection mold 36 between an open, closed, and clamped configuration, as generally described in U.S. Pat. No. Re. 37,827. The injection mold 36 is configured for high-volume, efficient lid production and accordingly includes an in-mold lid handling system 59. The in-mold lid handling system 59 is integrated into the injection molding process for receiving and transferring the lids (not shown) from the injection mold to a series of drop chutes, respectively, for the simple integration of an auxiliary processes, such as lid conveyance, stacking, and packaging.
The auxiliary process may include, as shown in FIG. 1, four lanes of lid conveyors 91, 92, 93, 94 with each lid conveyor lane dedicated to servicing a pair of drop chutes 77 provided to service each molding face 81, 82, 83, 84. Each lane of lid conveyors 91, 92, 93, 94 are positioned beneath the injection molding machine clamp unit 34 to align and engage with the corresponding drop chutes 77 in a mold closed position. The lid conveyors 91, 92, 93, and 94 may then subsequently transfer the lids (not shown) to a lid packing station 80 positioned behind the injection molding machine clamp unit 34.
The lid packing station may include a series of spin-bar lid stackers 96, one for each lane of lid conveyor 91, 92, 93, 94, for stacking the lids (not shown), thereafter the stacked lids 14 are transferred by means of a transfer robot 97 to a bagger 98 that bags and ejects the packaged stack of lids 16 onto a conveyor 99 for downstream handling into boxes.
In further detail, the injection mold 36 includes four molding faces 81, 82, 83, 84, that each include a pair of parallel rows of molding cavities. Each molding face 81, 82, 83, 84 is provided between a core plate assembly 60, 61 and a complementary cavity plate assembly 63. The cavity plate assembly 63 is shown in more detail with reference to FIG. 2. The core plate assemblies 60, 61 are provided by a center core plate assembly 61, and two single molding face core plate assemblies 60 mounted on the stationary and moving platens respectively. The faces of the core plate assemblies 60, 61, adjacent the molding faces 81, 82, 83, & 84, include core molding inserts 65 that provide a portion of the molding cavities. The cavity plate assemblies 63, adjacent the molding faces 81, 82, 83, & 84, include cavity molding inserts 67 that provide a complementary portion of the molding cavities to those of the core molding insert 65. The core and cavity plate assemblies are shown arranged such that a pair of cavity plate assemblies 63, henceforth referred to as a first and a second cavity plate assembly 63, are provided between each pair of the center core plate assembly 61 and a core plate assembly 60. The first and second cavity plate assemblies 63 are mounted on either side of a common hot runner 62. Each hot runner 62, of which there are two in a four-level mold, include a sprue bar 58, as shown in FIG. 2, for coupling the hot runner 62 to an injection unit (not shown) for supporting a flow of molding material, as is commonly known. For the sake of reference, the first and second cavity plate assemblies 63 and their hot runner 62 may collectively be referred to as a mold hot section 37.
Each molding face is serviced by the in-mold lid handling system 59. Accordingly, and with reference to FIG. 1, each mold hot section 37 includes a portion of the in-mold lid handling system 59 attached to its hot runner assembly 62. The in-mold lid handling system 59 includes a pair of vertically oriented slides 70 adjacent each molding face 81, 82, 83, 84 that are operable to translate laterally there across to retrieve a plurality of lids (not shown) from the corresponding vertical column of core molding inserts 65 and to thereafter transport the lids (not shown) to drop chutes 77. As shown in FIG. 2, each slide 70 is driven and guided by a dedicated transmission and servo motor 72 that are mounted to the hot runner 62. The slide 70 is typically a light weight rigid rail made from plastic or aluminum with a plurality of molded article retention devices, such as suction cups 71, mounted to a face thereof for engaging the lids 12 for transport. Each slide 70 may further include a vacuum channel (not shown) for connecting the suction cups 71 to a controllable vacuum source (not shown) that provides a means to controllably couple and decouple the lid to the suction cups 71.
As mentioned hereinbefore, the in-mold lid handling system 59 also includes a pair of drop chutes 77 adjacent each cavity plate assembly 63. With reference to FIG. 1, each pair of drop chutes 77 are shown mounted to a corresponding outer face of the hot runner 62 and positioned on either side of, and generally adjacent to, the cavity plate assemblies 63 in a substantially vertical orientation. With reference to FIG. 5, a typical drop chute 77 is shown. The drop chute 77 is a slender ‘U’-shaped channel with its open side facing a side edge of the lids 12 (not shown), that are being held on a slide 70, such that when the lids are translated to the outboard position they enter into the open side of the drop chute channel, as shown in FIG. 7. The drop chutes 77 further include guide cutouts 86 to provide clearance for the suction cups 71 of the slides 70 such that the lids 12 can be positioned generally completely within the drop chutes 77 before they are released from the suction cups 71.
With reference to FIG. 2, the in-mold lid handling system 59 is shown installed on a mold hot section for servicing a molding face 82, as shown in the direction 2—2 in FIG. 1, wherein each slide 70 is slidably connected to a face of the hot runner 62 by a dedicated transmission (i.e. drive shaft 73, driving gear 75, rack/linear rail 76, and linear bearing 74) and servo motor 72. Accordingly, each slide 70 includes a rack/linear rail 76 fastened at its ends, the rack/linear rails being oriented relative to the slide 70 to support a lateral translation of the slide 70 that is generally perpendicular to its longitudinal axis. The rack/linear rails themselves ride within linear bearings 74 that are attached to the front face of the hot runner 62. A rotational drive shaft 73, that includes a pair of driving gears 75 for engaging the rack portion of the rack/linear rail, is provided for driving each slide 70. The drive shaft being rotated, in use, by a dedicated servo motor 72. The detailed construction and operation of such an in-mold molded article handing system is provided in co-pending U.S. patent application Ser. No. 10/287,809. Of course, alternative in-mold lid handling systems could also have been used, such as the swing chutes described in U.S. Pat. No. 5,518,387.
In operation, the steps for retrieving and transferring the lids 12 from the mold 36 includes: laterally positioning of the slides 70 into an inboard position, as shown at reference symbol A in FIG. 2, such that the suction cups 71 are positioned in front of an exposed front face of the plurality of lids 12 held on the core molding inserts 65 (not shown); ejecting the plurality of lids 12 from the core molding inserts 65 onto the corresponding plurality of suction cups 71, the ejection action being provided by a plurality of mold stripper rings 65 (not shown) provided on the core plate assemblies; laterally positioning of the slides 70 into an outboard position, as shown at reference symbol B in FIG. 2, wherein the lids held thereon are positioned within a drop chute 77 (not shown); the lids 12 are thereafter released from the suction cups 72, for example by reversing the vacuum source to blow through the suction cups 71, and thereafter the lids 12 travel down within the channel of the drop chute, under the influence of gravity, for subsequent ejection into the auxiliary processes.
While the heretofore known in-mold lid handling systems 59 have succeeded in improving the efficiency and flexibility of lid molding systems, there remains the challenge of reducing the cost and complexity of such handling systems. Furthermore, the structural configuration and layout of many of such in-mold handling systems have introduced undesirable, and otherwise unnecessary, complexities and limitations of their own, that may include: complexities relating to mold installation; and restrictions relating to molding cavity pitch spacing and maximum mold cavitation (i.e. the number of molding cavities on the molding face).
In particular, there is a lot of expense associated with having to provide a dedicated servo motor 72 to drive each and every slide 70. With reference to FIG. 1, the four-level stack mold with its four molding faces 81, 82, 83, & 84 and two rows of molding cavities and hence slides 70 on each molding face, therefore requires eight servo motors 72. Furthermore, the linear bearings 74 and the linear rails 76 used in the in-mold lid handling system described hereinbefore, and as shown in FIG. 2, are typically expensive high-precision elements. The foregoing is of particular concern when a large number of such components is required, as it is for example with the four-level stack mold of FIG. 1 wherein sixteen sets of linear bearings 74 and linear rails 76 are required. Furthermore, the rack/linear rails 76 are quite large and are typically made from metal (e.g. aluminum and steel) and hence will have appreciable momentum with a the high rate with which the slides 70 shuttle between the inboard and outboard positions (i.e. high moving mass) that may limit system performance.
Again with reference to FIG. 2, complexities relating to injection mold 36 installation into the injection molding machine clamp unit 34 occur whenever it is intended to install the injection mold 36 vertically between the tie bars 56 of the clamp unit 34, as is common installation practice, and wherein the horizontal tie bar 56 spacing is larger than the width or the injection mold 36 but otherwise smaller than the width of the injection mold 36 including its in-mold lid handling system 59 installed thereon, as evaluated to the outermost extent of the outward projecting rack linear rails 76 in the outboard position. In such a situation, the rack/linear rails 76, in the outboard position, would interfere with the tie bars 56 during mold installation. Accordingly, injection mold 36 installation under such conditions would require at least a partial removal of the in-mold part handling system 59 from the injection mold 36, or may dictate that the injection mold 36 be installed in smaller portions thereof such that the slides 70 can be parked in the inboard position. Such requirements incur considerable costs in terms of increased time for mold installation, and therefore lost production, and the possibility of having to employ specialized skilled for the careful removal and re-installation of the in-mold lid handling system 59. Hence, it is undesirable to have an in-mold lid handling system with laterally projecting portions thereof that extend beyond the envelope of the injection mold 36, in the mold closed position.
Again with reference to FIG. 2, the injection mold 36 cavity pitch spacing and maximum mold cavitation may be significantly restricted by the placement and space required to accommodate the transmission (i.e. linear bearings 74 and linear rails) of the in-mold lid handling system 59. For example, the vertical placement of the linear rails 76 is dictated by the tie bars 56 such that there is no interference between the two whenever the linear rails 76 are positioned in the outboard position. Accordingly, the vertical space available for the placement of molding cavities is thereby restricted.
Hence, there is a need to provide a simplified and relatively inexpensive in-mold handling system for molded article. Furthermore, there is a need for an in-mold handling system 59 that doesn't complicate injection mold 36 installation into the machine clamp unit 34, and that dictates relatively minimal restrictions relating to molding cavity pitch spacing and maximum mold cavitation.